PROJECT SUMMARY/ABSTRACT Coxsackievirus B (CVB), a member of the enterovirus family of RNA viruses, is associated with a number of diverse syndromes, including meningitis, pericarditis, febrile illness, diabetes, dilated cardiomyopathy and myocarditis. A key event in CVB pathogenesis is the induction of host cell death. Enteroviruses are lytic viruses and possess no known mechanism for progeny release other than the destruction of the host cell membrane. However, cell death induction must be balanced precisely as activating cell death prematurely, or by alternative pathways, could inhibit replication and/or induce inflammatory signaling. Whereas CVB commonly induces apoptosis in many non-polarized cell types, we have shown that CVB-infected polarized intestinal epithelial cells undergo necrosis, which is required for virus egress. However, the molecular basis for this difference has remained elusive. In this proposal, we will extend our previous studies to provide a mechanistic understanding of the pathways that mediate CVB- induced intestinal cell death and how these pathways might affect CVB pathogenesis and inflammatory signaling. We will (1) define the role of the pro-necrotic serine/threonine nonreceptor kinase receptor-interacting protein 3 (RIP3) in CVB-induced necrotic cell death of the intestinal epithelium, (2) define the mechanisms employed by CVB to attenuate RIP3- mediated signaling, and (3) define the role of necrotic cell death in CVB-induced destruction of the epithelial barrier and inflammatory signaling. These studies provide critical insights into the molecular events that promote necrotic signaling in response to CVB, and possible other RNA virus, infection within the intestinal epithelium. In addition, these studies will identify previously unknown host targets that could be targeted to enhance antiviral defenses and/or limit CVB- induced egress from and inflammation of the gastrointestinal tract.